1.625 IIRC. I also ran some springs that were 1.650. Those went in at 2.100 as I screwed up. I should have stayed at 2.000 but thought I'd get more lift than I did.
Mandatory spring cups for any X head, j still hanging off the spring seats barely with a comp 917 1.55 spring. Those are 200@1.80/596@1.100 or .700 566 rate...I stick them in around 1.78.
W2 is different of course, but the production pass car heads are all different spring seat OD...x heads are oval on most and vary 1.4195 -1.450, machine them down for some spring and seals and the some get 1.560 at the oval.. j heads got bigger..still kinda ovaled seats..1.525
Then the rockers, the push rods like you said...move the rocker , grind the rocker and use fatter pushrods and now the p.r holes in the head need opened up.
I like to avoid that if I can.
1.62 springs ...you could say ,would be another reason to buy some trick flows. Better rocker placement, fit more spring, more room.. just plain better everywhere.